The present invention relates to a power window switch circuit, and more particularly, it relates to a power window switch circuit having a drive motor, a relay, a switch and the like for raising and lowering a window glass.
In general, a vehicle has a power window apparatus for opening and closing a window glass of a side door and the like, and the power window apparatus includes an UP switch (raising switch) and a DOWN switch (lowering switch) manually operated for raising and lowering the window glass.
FIG. 1 schematically shows an electric circuit of a power window switch circuit 10 in a conventional power window apparatus. The power window switch circuit 10 includes a DOWN switch 28, an UP switch 29, an automatic switch 30, a control circuit 12, a drive circuit 20, and a drive motor M which is preferably a DC motor for raising and lowering a window glass. The drive circuit 20 includes a first relay 22, a second relay 24, and transistors TR1 to TR3. The DOWN switch 28 and the UP switch 29 are used, for example, as a tumbler two-stepped click type switch. The DOWN switch 28 has a first knob (hereinafter referred to as xe2x80x9cthe DOWN side knobxe2x80x9d), and a second knob (hereinafter referred to as xe2x80x9cthe UP side knobxe2x80x9d). When the DOWN side knob is pressed by one step, a movable contact 31 of the DOWN switch 28 is connected to a fixed contact DN. When the UP side knob is pressed by one step, a movable contact 32 of the UP switch 29 is connected to a fixed contact UP. When the DOWN side knob is pressed by two steps, the DOWN switch 28 and the automatic switch 30 are both turned on. Moreover, when the UP side knob is pressed by two steps, the UP switch 29 and the automatic switch 30 are both turned on. In the automatic operation, after the knob is pressed by two steps, the DOWN switch 28 or the UP switch 29 is turned off but the automatic switch 30 is maintained in ON state for a predetermined period of time.
When the automatic switch 30 and the DOWN switch 28 are turned on, the control circuit 12 continues to supply a high (H) level relay drive signal to the base of the transistor TR3 even after the DOWN switch 28 is turned off, until the window glass reaches a completely open position, and supplies an ON signal to the base of the transistor TR1, thereby turning on the transistors TR1 and TR3. This supplies excitation current to the relay coil 21 of the first relay 22. When the relay coil 21 is excited, the movable contact 25c of the relay contact 25 is switched from a ground side fixed contact 25a to a power supply side fixed contact 25b, and the drive motor M is supplied with the drive current and rotated in normal direction. The drive motor M drives a wire-type or arm-type regulator (not shown) so as to lower the window glass. When the window glass reaches the completely open position, a completely open position limit switch (not depicted) begins to operate. In response to this switch operation, the control circuit 12 stops drive of the drive motor M by the relay drive signal and maintains the window glass at the completely open position.
When the automatic switch 30 and the UP switch 29 are turned on, the control circuit 12 continues to supply a high (H) level relay drive signal to the base of the transistor TR2 even after the UP switch 29 is turned off, until the window glass reaches a completely closed position, and supplies an ON signal to the base of the transistor TR1, thereby turning on the transistors TR1 and TR2. This supplies excitation current to the relay coil 23 of the second relay 24. When the relay coil 23 is excited, the movable contact 26c of the relay contact 26 is switched from a ground side fixed contact 26a to a power supply side fixed contact 26b, and the drive motor M is rotated in reverse direction. The drive motor M drives the regulator (not shown) so as to raise the window glass. When the window glass reaches the completely closed position, a completely closed position limit switch (not shown) begins to operate. In response to this switch operation, the control circuit 12 stops drive of the drive motor M by the relay drive signal and maintains the window glass at the completely closed position.
When the DOWN side knob is operated to turn on the DOWN switch 28, the control circuit 12 supplies a high (H) level relay drive signal to the base of the transistor TR3 and supplies the ON signal to the base of the transistor TR1, thereby turning on the transistors TR1 and TR3. Accordingly, while the DOWN switch 28 is in ON state, excitation current is supplied to the relay coil 21 and drive motor M is rotated in the normal direction, thereby lowering the window glass.
When the UP side knob is operated to turn on the UP switch 29, the control circuit 12 supplies the high (H) level relay drive signal to the base of the transistor TR2 and supplies the ON signal to the base of the transistor TR1, thereby turning on the transistors TR1 and TR2. Accordingly, while the UP switch 29 is in ON state, excitation current is supplied to the relay coil 23 and drive motor M is rotated in the reverse direction, thereby raising the window glass.
When the first relay 22, the second relay 24, and the control circuit 12 are soaked by an electrolyte liquid such as rain, leak resistance R11 to R15 may be caused as shown by dotted lines in FIG. 1.
For example, even if the DOWN switch 28 is turned off and the control circuit 12 does not supply the ON signal and the H level relay drive signal to the transistors TR1 and TR3, respectively, the transistors TR1 and TR3 are turned on by the leak resistance R11 and R13. This excites the relay coil 21, and the movable contact 25c is connected to the power supply side fixed contact 25b, which rotates the drive motor M in the normal direction and unintentionally lowers the window glass.
Moreover, even if the UP switch 29 is turned off and the control circuit 12 does not supply the ON signal and the H level relay drive signal to the transistors TR1 and TR2, respectively, the transistors TR1 and TR2 are turned on by the leak resistance R11 and R12. This excites the relay coil 23, and the movable contact 26c is connected to the power supply side fixed contact 26b, which rotates the drive motor M in the reverse direction and unintentionally raises the window glass.
Furthermore, even if the transistor TR3 is in OFF state, generation of leak resistance R11 and R15 may excite the relay coil 21, which in turn rotates the drive motor M in the normal direction to lower the window glass unintentionally. Furthermore, even if the transistor TR2 is in OFF state, generation of leak resistance R11 and R14 may excite the relay coil 23, which in turn rotates the drive motor M in the reverse direction to raise the window glass unintentionally.
When the leak resistance R11 to R13 are generated, the transistors TR1 to TR3 are turned on, the relay coils 21 and 23 are excited, and the movable contacts 25c and 26c are connected to the power supply side fixed contacts 25b and 26b, respectively. In this case, identical voltage is applied to both the terminals of the drive motor M. Accordingly, even if the DOWN side knob or the UP side knob is operated, the drive motor M is not driven and the window glass is not raised or lowered.
When the leak resistance R11, R14, and R15 are generated, the transistor TR1 is turned on by the leak resistance R11, the relay coils 21 and 23 are excited, and identical voltage is applied to both the terminals of the drive motor M. Accordingly, even if the DOWN side knob or the UP side knob is operated in this state, the drive motor M is not driven and the window glass is not raised or lowered.
As has been described above, depending on the position where leak resistance is generated, four possible states should be considered: (a) only the UP side relay coil 23 is excited; (b) only the DOWN side relay coil 21 is excited; (c) both of the relay coils 21 and 23 are excited; (d) neither the relay coils 21 nor 23 is excited. Accordingly, when the power window switch circuit 10 is soaked, it cannot be decided whether the window glass is raised or lowered. As a result, movement of the power window switch circuit 10 which is operated by a person in the vehicle cannot be properly achieved.
It is therefore an object of the present invention to provide a power window switch circuit which can prevent theunintentional raising or lowering of a window glass when the power window switch circuit is soaked.
According to a first embodiment of the present invention, there is provided a power window switch circuit which includes a first relay coil having two terminals; a down switch connected to the first relay coil for lowering a window glass; a second relay coil having two terminals; and an up switch connected to the second relay coil for raising a window glass. Each of the down switch and the up switch includes a first fixed contact connected to a power supply; a second fixed contact connected to the ground; and a movable contact selectively connecting one of the first and the second fixed contact to a first terminal of the corresponding relay coil. A first switching element responsive to a soak detection signal is connected between the second fixed contacts of the down switch and the up switch and the ground. The first switching element is also connected between second terminals of the first and second relay coils and the ground. The power window switch circuit further includes a soak detection circuit for supplying the soak detection signal to the first switching element when detecting the soak.
According to a second embodiment of the present invention, there is provided a power window switch circuit which includes a first relay coil having two terminals; a down switch connected to the first relay coil for lowering a window glass, a second relay coil having two terminals; and an up switch connected to the second relay coil for raising the window glass. The down switch includes a first fixed contact connected to a power supply; a second fixed contact connected to a first terminal of the first relay coil; and first and second movable contacts corresponding to the first and second fixed contacts. The up switch includes a third fixed contact connected to a power supply; a fourth fixed contact connected to a first terminal of the second relay coil; and third and fourth movable contacts corresponding to the third and fourth fixed contacts. A first switching element is connected between the first movable contact of the down switch and a first terminal of the first relay coil. A second switching element is connected between the third movable contact of the up switch and a first terminal of the second relay coil. A third switching element is connected between the second and fourth movable contacts of the down switch and the up switch and the ground. The third element turns on one of the first and second switching elements when turned on in response to a soak detection signal. The power window switch circuit further includes a soak detection circuit for supplying the soak detection signal to the third switching element when detecting the soak.